A number of chemical disinfectants and sterilants are in use in healthcare institutions, including ethylene oxide, compositions of aldehydes, especially, formaldehyde, and dialdehyde (e.g., glutaraldehyde). More recently, hydrogen peroxide solutions have found a limited use for disinfection. Disinfection, as used herein, refers to the destruction of vegetative microorganisms and viruses and typically some spores; sterilization refers to the total destruction of all life forms, specifically, including spores.
Hydrogen peroxide (H.sub.2 O.sub.2) is known as a potent non-irritating germicide that has been used as a topical antiseptic, especially in a 3% aqueous solution. However, hydrogen peroxide solutions are known to be corrosive to metal and inherently unstable. Practitioners in the art have sought to utilize higher concentrations of hydrogen peroxides for disinfection and sterilization of medical instruments while attempting to control its corrosiveness to metals and improve stability. Hydrogen peroxide decomposes to water and oxygen. This process is catalyzed by the enzyme catalase, which is present in organic matter such as that which is typically found on instruments after medical or dental procedures. This organic matter if not removed during routine instrument cleaning will accelerate the decomposition process and ultimately shorten the useful life of the germicide solution.
The stability of hydrogen peroxide is known to be enhanced by the presence of acids which are believed to denature and therefore prevent the catalytic effect of the catalase. U.S. Pat. No. 4,051,059, incorporated herein by reference, describes a peroxyacid antimicrobial composition of hydrogen peroxide, peracetic acid, acetic acid and a surfactant such as sulfonates or sulfates. Similarly, U.S. Pat. No. 5,200,189, the disclosure of which is incorporated herein by reference, describes a peroxyacid antimicrobial composition comprised of a C1-C4 peroxycarboxylic acid, hydrotrope coupling agent, and hydrogen peroxide. Such solutions, however, are too corrosive to be useful in a number of environments.
Still other compositions have been described which include hydrogen peroxide in conjunction with a substituted aminobenzaldehyde as an organic stabilizer and mineral acid, as an etching agent. See, U.S. Pat. No. 4,875,973, incorporated herein by reference. Alternatively, antimicrobial compositions are provided in U.S. Pat. No. 5,077,008, incorporated herein by reference, in which a strong oxidizing agent is combined with peracetic acid; chlorine releasing compounds; a copper and brass corrosion inhibitor in the form of triazoles, azoles, and benzoates; a buffering agent; a carbon steel and aluminum corrosion inhibitor in the form of chromates, borates, dichromates, molybdates, vanadates, phosphates, and tungsates; a wetting agent; and a sequestering agent. This composition is designed to be dissolved in water and utilized with a sterilizer device to control process temperature, fluid pressure, contact time, and water purity.
Other peroxides have also been described for use as preservatives, sterilants or disinfectants. U.S. Pat. No. 5,147,884, incorporated herein by reference, describes a preservative for aqueous products and systems comprising tert-butyl hydroperoxide, a monophenyl glycol ether, an organic solvent or mixture of water and organic solvent, a biocide in the form of non-halogenated phenol, a urea derivative and a surface active agent.
Compositions which have addressed both the stability and corrosiveness of the hydrogen peroxide/organic peracids have also been described. In particular, U.S. Pat. No. 4,518,585 provides hydrogen peroxide compositions (ENDO-SPOR.RTM.) which are noted to be stable with reuse over an extended period of time. The disinfectant and sterilizing solution described comprises hydrogen peroxide, a surfactant compatible with hydrogen peroxide, an aqueous-alcoholic mixture of a tertiary amine and a fatty acid alkanolamide, and an organic triazole corrosion inhibitor which is non-irritating with in-use stability.
A number of corrosion inhibitors are known to be only slightly soluble in aqueous solutions and the effectiveness of the overall composition is therefore limited.
What is needed in the art are new compositions which are useful for disinfecting and sterilizing metal, ceramic, polymeric and elastomeric surfaces, especially medical and dental equipment, but which are stable for longer shelf-life and under heavy organic loading and which provide increased anti-corrosive properties. Surprisingly, the present invention provides such compositions.